diff --git a/lib/isc/include/isc/netmgr.h b/lib/isc/include/isc/netmgr.h
index 6c52f638c8..671880137d 100644
--- a/lib/isc/include/isc/netmgr.h
+++ b/lib/isc/include/isc/netmgr.h
@@ -697,3 +697,6 @@ isc__nm_force_tid(int tid);
  * Force the thread ID to 'tid'. This is STRICTLY for use in unit
  * tests and should not be used in any production code.
  */
+
+void
+isc_nmhandle_setwritetimeout(isc_nmhandle_t *handle, uint64_t write_timeout);
diff --git a/lib/isc/netmgr/netmgr.c b/lib/isc/netmgr/netmgr.c
index b63f990163..ddcfe23276 100644
--- a/lib/isc/netmgr/netmgr.c
+++ b/lib/isc/netmgr/netmgr.c
@@ -604,6 +604,14 @@ isc_nm_maxudp(isc_nm_t *mgr, uint32_t maxudp) {
 	atomic_store(&mgr->maxudp, maxudp);
 }
 
+void
+isc_nmhandle_setwritetimeout(isc_nmhandle_t *handle, uint64_t write_timeout) {
+	REQUIRE(VALID_NMHANDLE(handle));
+	REQUIRE(VALID_NMSOCK(handle->sock));
+
+	handle->sock->write_timeout = write_timeout;
+}
+
 void
 isc_nm_settimeouts(isc_nm_t *mgr, uint32_t init, uint32_t idle,
 		   uint32_t keepalive, uint32_t advertised) {